Connecticut regulators have sided with the state’s two largest utilities in their dispute with environmental advocates who accused them of restricting gas capacity, costing consumers billions of dollars.

The state Public Utilities Regulatory Authority said in a recent decision it “has not found any evidence that the (utilities) failed to manage their gas supply portfolios on the peak demand days for these winter periods using prudent strategies and in accordance with authority directives and expectations.”

Researchers for the Environmental Defense Fund wrote in the summer of 2017 that they found evidence the gas and electricity utilities regularly restricted capacity to New England by scheduling deliveries “without actually flowing gas.” Consumers paid an estimated $3.6 billion in “artificially inflated bills” over three years, EDF said.

Researchers said they found a “distinctive pattern” of Eversource and Avangrid, the parent company of United Illuminating, routinely ordering day-long large deliveries, then sharply reducing the orders “at the last minute.” The result was to limit available gas supply, leading to price spikes.

They cited the winter of 2013-14 when temperatures plunged with a blast of Arctic air that drifted south, known as the “polar vortex.” Gas prices on Jan. 22, 2014 were nearly four times that of a benchmark price, they said.

Eversource said in a statement that the regulators' decision “essentially reaffirms what we and other regulatory agencies and experts have been stating all along — that the claims made by the EDF were patently false and misleading.”

A spokesman for United Illuminating did not immediately respond to an email seeking comment.

Jon Coifman, a spokesman for EDF, said the environmental group has not accused the utilities of violating any laws, but said the companies “acted in a way that had the effect of raising prices” for individual and business consumers.

N. Jonathan Peress, senior director of energy market policy at EDF, said improved transparency, new pricing structures and “better alignment of risks and rewards” will improve competitiveness and help drive new innovation. New policies also will "provide a more honest picture of the true need for new gas supply capacity and the most cost-effective ways to meet it,” he said.

The decision by state regulators is similar to the results of a staff inquiry of the Federal Energy Regulatory Commission that found “no evidence of anti-competitive withholding of natural gas pipeline capacity by New England shippers.”